What a load of crap! There is still tons of "mainstream media" outlets that don't do this. One of the biggest in the UK would be The Guardian, there are hundreds like it.
The decision to toe the line, like the WaPo, are purely because of money (Jeff's and his readership's), not because anyone is "shutting them down" for X or Y.
Your last point seems to be the parent's point as well -- if you want to keep your media business alive (to make money; that's what businesses are) in the US you have to be careful criticizing those currently in power. Unless I misunderstood you to and you meant that parroting the party line is a way to make more money but not doing it is also perfectly effective and not at all a risk.
Alternative voices are to be found on tight corners of the internet, like an individual on Twitter for example.
I used to like the Guardian in 2009-214 but now, I trust someone's "it came to me in a dream", before I trust The Guardian, given their recent flops and biases.
So much wisdom on comedy, even 80s comedy Who reads the papers? - Yes, Prime Minister - BBC comedy: https://www.youtube.com/watch?v=DGscoaUWW2M